The invention relates to an apparatus for testing the leaktightness of filled, closed packages of flexible material, comprising conveyor means for feeding the packages in line, means for applying pressure to the packages while they are being conveyed, whereby packages free from leaks are locally expanded by the pressure and leaking packages are subjected by the pressure to expansion either not at all or to a far lesser extent, and means for determining the amount of the local expansion.
An apparatus of this kind is known from U.S. Pat. No. 4,024,956. This known apparatus is particularly intended for testing packets of cigarettes. The conveyor means consist of two conveyor belts acting on the sides of the packets and causing the latter to slide over a fixed support. The means applying pressure to the packets consist of adjustable brackets which press the conveyor belts against the sides of the packets, and of pressure rollers which act on the top face of the packets. These rollers are intended to force air out of any leaking packets. The pivoting arm is disposed downstream of the pressure rollers, referring to the direction in which the packets are conveyed. At the moment when the pivoting arm acts on the packets, the latter are compressed only by the side conveyors. An apparatus of this kind would be unsuitable for testing bags having two curved faces which are joined together by three or four sealing seams. Bags of this kind are usually employed for packing potato crisps, salted crackers, and the like. A pivoting arm acting on a sealing seam would have little effect. With bags of this kind, perfect testing for leaks makes it necessary for the bags to be compressed over a large area and for the pivoting arm to act on a small part of one of the two faces, this part being held taut when there are no leaks.